(Radio Iowa) – The head of the National Security Agency told members of a U.S. Senate committee on Wednesday the agency’s in-depth surveillance of American citizens has stopped dozens of terrorist attacks. Iowa Senator Tom Harkin remains unconvinced.

“That’s one thing I just don’t accept on its face value,” Harkin says. “They say that, of course they’re going to say that because they’re covering their you-know-what. They’re going to say ‘We thwarted this, we thwarted that,’ well, how are you ever going to prove something like that? I’d really have to see more proof than just their word.”

The NSA commander, General Keith Alexander, was questioned before the panel about the agency’s gathering of data from our phone calls, emails and internet activity. Harkin says it’s troubling.

“The government is going beyond its bounds, putting a kind of fear out there among people about who they can call and what they can say and is the government listening and will this be recorded?” Harkin says. “That has a real chilling affect and I don’t think it’s healthy.”

General Alexander told members of the Senate Appropriations Homeland Security Committee that his agency has done nothing wrong, but Harkin questions whether the restrictions of the Patriot Act were left in the rear-view mirror. “I’m just not going to accept the word of the head of the NSA or the head of some of our intelligence agencies,” Harkin says.

“I’ve had dealings with them over the past 30 years in which I’ve seen our intelligence agencies manipulate and twist information to their own ends.” Harkin, a Democrat, says President Obama needs to take more of a leadership role in this deepening dilemma.

“If I had one bit of advice for the president I’d say: ‘Get a handle on this. You run these agencies,’” Harkin says. “Maybe some heads ought to roll.”